The present invention relates to electrophotography, more specifically, to electrophotographic imaging members.
In electrophotography, an electrophotographic member containing a photoconductive insulating layer on a conductive layer is imaged by first uniformly electrostatically charging its surface. The member is then exposed to a pattern of activating electromagnetic radiation such as light. The radiation selectively dissipates the charge in the illuminated area of the photoconductive insulating layer while leaving behind an electrostatic latent image in the non-illuminated area. This electrostatic latent image may then be developed to form a visible image by depositing finely divided toner particles on the surface of the photoconductive insulating layer. The resulting visible image may then be transferred from the electrophotographic member to a support such as paper. This imaging process may be repeated many times with reusable photoconductive insulating layers.
An electrophotographic imaging member may be provided in a number of forms. For example, the imaging member may be a homogeneous layer of a single material or may be a composite layer containing a photoconductor and other material(s). A multilayered photoreceptor, for example, may comprise a substrate, a conductive layer, a blocking layer, an adhesive layer, a charge generating layer and a charge transport layer. Examples of photosensitive members having at least two electrically operative layers include a charge generator layer and a diamine containing transport layer as disclosed in U.S. Pat. Nos. 4,265,990; 4,233,384; 4,306,008; 4,299,897; and 4,439,507.
In multilayered imaging members, materials used for each layer preferably have desirable mechanical properties while also providing electrical properties necessary for the function of the device. If the material of one layer of the imaging device is changed in an attempt to improve a particular property, for example an electrical property, the change may have an adverse effect on mechanical properties, for example, such a change may lead to delamination. In the barrier (charge blocking) layer of multilayered imaging devices, it is desirable to provide a material which prevents charge injection while also preventing migration of materials, such as charge transport compounds, through the charge blocking layer.
Other difficulties exist in the fabrication of imaging members. For example, in seamless imaging members, a conductive metal layer cannot be deposited in an economic manner. Vacuum coating techniques are expensive when employing seamless substrates. Thus, the use of conductive layers applied by other coating techniques becomes important.
Recent work has indicated that seamless photoreceptors having conductive substrates of nylon with carbon black particles dispersed therein provide attractive properties. However, such photoreceptors may suffer from unsatisfactory adhesion and poor mechanical properties.
U.S. Pat. No. 3,887,369 to Matsuno et al discloses a barrier layer of copolymers comprising alkyl vinyl ethers and maleic anhydride, or composites of alkyl vinyl ethers/alkyl half esters of maleic acid copolymers and polyvinyl pyrrolidone or copolymers thereof.
U.S. Pat. No. 4,579,801 to Yashiki discloses an electro-photographic photosensitive member having a phenolic resin layer formed from a resol coat, between a substrate and a photosensitive layer. The phenolic resin layer may contain a dispersed electrically conductive material. Carbon is mentioned as an electrically conductive material.
U.S. Pat. No. 4,571,371 to Yashiki discloses an electrophotographic photosensitive member having an electroconductive layer between a substrate and a photosensitive layer. The electroconductive layer contains electroconductive material, a binder resin and a silicone compound leveling agent. Carbon powder is mentioned as an electroconductive material, and phenolic resin is mentioned as a binder resin. The silicone compound leveling agent allegedly improves the interfaces between the electroconductive layer and both the substrate and the photosensitive layer.
U.S. Pat. No. 4,296,190 to Hasegawa et al discloses an ionizing radiation curable resin such as non-modified maleic anhydride type unsaturated polyester, as an electrophotographic sensitive material. This material may be applied as a solution to a conductive substrate.
The above-described devices suffer from a number of disadvantages. For example, some electrophotographic imaging members suffer from poor charge acceptance and an excess of charge injections. In addition, charge transport materials from the photosensitive layer may diffuse and come in contact with the conductive layer, adversely affecting the photoreceptor. Additional problems of prior art imaging members include cycling up of electrical data during extended cycling in a scanner and excessive original residual voltage after erasing.